JP2000176777A - Spindle head control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect the damage of a protective bearing when a used tool is extracted from a main spindle by moving the main spindle to the front side in the axial direction at the time of a tool change by a tool change means, coupling a coupling member and the protective bearing, and constraining the movement of the main spindle to the front side in the axial direction. SOLUTION: When a bearing control means 41 receives a tool change start signal in a vertical machining center, the feed power to the rear stator 32 of a thrust magnetic bearing 30 is reduced, and the feed power to a front stator 35 is increased. A main spindle 3 is moved to the front side in the axial direction, and a nut 9 is brought into contact with a rear angular ball bearing 8. A tool T fitted to the main spindle 3 is extracted by the operation of a tool change means in this state, then a new tool T is fitted to the main spindle 3. Since the nut 9 screwed to the rear end section of the main spindle 3 is already kept in contact with the rear ball bearing 8, the main spindle 3 is prevented from being moved further to the front side in the axial direction, and the collision between the nut 9 and the ball bearing 8 is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool provided with a spindle head for supporting a spindle by a magnetic bearing and a tool changing means for exchanging a tool mounted on the spindle with a new tool. How to control.

[0002]

2. Description of the Related Art FIG. 4 shows a vertical machining center as an example of the machine tool in which a main shaft is supported by magnetic bearings. FIG. 4 is a front view partially showing a main part of a conventional vertical machining center in a block diagram with a spindle head portion as a center.

As shown in FIG. 4, the (vertical) machining center 1 comprises a spindle head 2 for rotatably supporting a spindle 3, a bearing control means 41 for controlling the operation of the spindle head 2, and the spindle. 3 is provided with a tool exchange means (not shown) for exchanging the tool T mounted on 3 with a new tool T.

[0004] The spindle head 2 includes a spindle 3 whose axis is oriented vertically, a rear radial magnetic bearing 10 that radially supports a rear side (upper side) of the spindle 3,
A front radial magnetic bearing 20 that also supports the front side (lower side) of the main shaft 3 in the radial direction, and between the rear radial magnetic bearing 10 and the front radial magnetic bearing 20,
A thrust magnetic bearing 30 that supports the main shaft 3 in the axial direction, a rear angular ball bearing 8 provided on the rear side of the rear radial magnetic bearing 10, and a front part provided on the front side of the front radial magnetic bearing 20. Angular contact ball bearings 5,
A nut 9 screwed to the rear end of the main shaft 3.

Although not particularly shown in FIG. 4, a tapered receiving portion for receiving the tapered portion of the tool T is formed at the front end of the main shaft 3, and the tapered portion of the tool T is formed in this receiving portion. The tool T is mounted on the main shaft 3 by being inserted.

Further, between the rear radial magnetic bearing 10 and the rear angular ball bearing 8, four sensors 16 for detecting the position of the main shaft 3 in the radial direction are provided in the same plane in the radial direction. Between the magnetic bearing 20 and the front angular contact ball bearing 5, four sensors 25, which are also provided on the same plane in the radial direction and detect the position of the spindle 3 in the radial direction, and detect the position of the spindle 3 in the axial direction Two sensors 39 are provided.

In FIG. 1, reference numeral 4 denotes a drive rotor, which constitutes a part of a built-in drive motor for rotating the main shaft 3 about the axis. The stator of the drive motor and the components of the spindle head 2 are supported by a housing (not shown).

The rear radial magnetic bearing 10 includes a rotor 14 formed by laminating a ring-shaped metal plate, a holding member 15 for holding the rotor 14, a laminate 12 formed by laminating the metal plates, and The holding member 15 has an inner diameter portion fitted and fixed to the main shaft 3, and the holding member 15 is fixed to the stator 11. It is held in a housing (not shown). Further, the four stators 11 are evenly arranged along the outer peripheral surface of the rotor 14, and the four sensors 16 are also disposed along the outer peripheral surface of the main shaft 3, and They are evenly arranged with a corresponding relationship. A gap (air gap) of, for example, about 0.5 mm is provided between the stator 11 and the rotor 14.

The front radial magnetic bearing 20 includes a rotor 24 formed by laminating ring-shaped metal plates, a laminate 22 similarly formed by laminating metal plates, and a laminate 22 formed by laminating metal plates.
The rotor 24 has an inner diameter portion fitted and fixed to the main shaft 3 and the stator 21 is fixed to the housing (not shown). ) Is held. Further, the four stators 21 are evenly arranged along the outer peripheral surface of the rotor 24, and the four sensors 25 are also disposed along the outer peripheral surface of the main shaft 3, with the stator 21. They are evenly arranged with a corresponding relationship. As in the rear radial magnetic bearing 10, the stator 21
A gap (air gap) of, for example, about 0.5 mm is also provided between the rotor and the rotor 24. In addition, the spindle 3
Are formed with two flange portions 6 and 7. The outer peripheral surface of the flange portion 7 is detected by the sensor 25, and the lower end surface thereof is detected by the sensor 39. The front side of the rotor 24 is locked by the flange 6.

The thrust magnetic bearing 30 includes a rear stator 32 having a rotor 31 having an inner diameter portion fitted and fixed to the main shaft 3, a coil 33 formed in a ring shape, and a holding ring 34 holding the coil 33. And a front stator 35 comprising a coil 36 also formed in a ring shape and a holding ring 37 for holding the coil 36, and a spacer 38 provided between the rear stator 32 and the front stator 35. A flange portion 31a is formed on an outer peripheral portion of the rotor 31. The flange portion 31a
Are located between the rear stator 32 and the front stator 35. Also, a gap (air gap) of, for example, about 0.5 mm is provided between the flange portion 31a and the rear stator 32 and between the flange portion 31a and the front stator 35.

The angular ball bearings 5 and 8 are provided so as to have an air gap (air gap) of, for example, about 0.2 mm between the inner ring portion and the main shaft 3. The angular ball bearing 8 and the nut 9 is provided with a similar gap, and does not function as a bearing in a normal state. For example, when an unexpected abnormality such as a power failure or failure occurs, the main shaft 3 is moved in the radial direction. The stator 11, 21 and the rear stator 3 are supported in the axial direction.
2. It serves as a protective bearing for preventing the front stator 35 and the rotors 14, 24, 31 from being damaged. For this reason, the angular ball bearings 5, 8
The air gap in the rear radial magnetic bearing 1
0, front radial magnetic bearing 20 and thrust magnetic bearing 3
It is smaller than the air gap at zero.

The bearing control means 41 supplies predetermined electric power to the coils 13, 23, 33, and 36 of the rear radial magnetic bearing 10, the front radial magnetic bearing 20, and the thrust magnetic bearing 30, respectively. Sensor 1
The current supplied to the coils 13, 23, 33, 36 is adjusted in accordance with the displacement of the main shaft 3 detected by 6, 25, 39.

When predetermined power is supplied from the bearing control means 41 to the coils 13, 23, 33, and 36, the stator 11 of the rear radial magnetic bearing 10, the stator 21 of the front radial magnetic bearing 20, and The rear stator 32 and the front stator 3 of the thrust magnetic bearing 30
5 each become an electromagnet, and thereby the rotor 1
4, 24 and 31 are respectively sucked.

In the rear radial magnetic bearing 10, the four stators 11 apply suction force in four directions to the rotor 14, and in the front radial magnetic bearing 20, similarly, the four stators 21 generate four directions of attractive force. Attraction force acts on the rotor 24, and the main shaft 3 is radially supported by the rear radial magnetic bearing 10 and the front radial magnetic bearing 20.

As described above, the sensors 16 and 2
5, the radial position of the main shaft 3 is detected. When the main shaft 3 deviates from the neutral position between the stators 11 and when the main shaft 3 deviates from the neutral position between the stators 21, this positional deviation Sensor 16 and sensor 25
Respectively, and based on this detection signal,
The power supplied to each of the stators 11 and the stator 21 is adjusted by the bearing control means 41. That is, the distance between each stator 11 and the rotor 14 and each stator 21
In the space between the rotor and the rotor 24, the power supplied to the stator 11 and the stator 21 whose space is wider than the reference space is increased and the suction force is increased, while the space is larger than the reference space. The power supplied to the narrowed stator 11 and stator 21 is reduced, and the suction force is reduced. Thus, the main shaft 3 is always located between the stators 11 and the stator 2.
It is controlled so as to be located at a neutral position between one.

Further, in the thrust magnetic bearing 30, the rear stator 32 and the front stator 35 cause the flange portion 31a of the rotor 31 to receive suction force in both front and rear (up and down) directions.
It is supported in the axial direction so as to be located at an intermediate position between the front stator 2 and the front stator 35.

As described above, the main shaft 3 is detected by the sensor 39.
Is detected in the axial direction, and when the main shaft 3 is displaced from the intermediate position between the rear stator 32 and the front stator 35, the displacement is detected by the sensor 39, and based on this detection signal, The rear stator 32
The electric power supplied to the front stator 35 is adjusted by the bearing control means 41. That is, in the interval between the rear stator 32 and the flange portion 31a of the rotor 31, and in the interval between the front stator 35 and the flange portion 31a, the rear stator 3 is wider than the reference interval.
The power supplied to the second or front stator 35 is increased to increase the attraction force, while the power is supplied to the rear stator 32 or the front stator 35 whose interval is narrower than the reference interval. The power is reduced and the suction force is reduced. Thus, the rotor 3
1 is always controlled to be located at an intermediate position between the rear stator 32 and the front stator 35, whereby the main shaft 3 is properly supported in the axial direction.

According to the machining center 1, the main shaft 3 is supported in the radial and axial directions by the attractive force of the electromagnet without directly contacting the main shaft 3, so that it rotates at an extremely high rotational speed. The main shaft 3 can be properly supported.

When the tool T mounted on the spindle 3 is replaced with a new tool T, the rotation of the spindle 3 is stopped, and the used tool T mounted on the spindle 3 is replaced by the tool replacement. Then, a new tool T is mounted on the spindle 3 by the tool changing means (not shown). At this time, the main shaft 3 is supported in the axial direction by the thrust magnetic bearing 30 so as to be located at the neutral position.

[0020]

However, in the conventional machining center 1 described above, when the used tool T mounted on the spindle 3 is pulled out by the tool changing means (not shown), the tool is replaced. Due to the close contact between the tapered portion of the tool T and the receiving portion of the main shaft, the main shaft 3 is moved together with the tool T in the pulling-out direction, that is, in the axial front portion, whereby the nut 9 screwed to the rear end of the main shaft is angularly moved. A collision with the ball bearing (protective bearing) 8 causes a problem that the angular ball bearing 8 is damaged.

Normally, the tool T is firmly fixed to the receiving portion of the main shaft 3 by pulling the pull stud of the tool T by a collet chuck or the like and pulling the tool T by a draw bar or the like connected to the collet chuck.
Therefore, the tapered portion of the tool T has an extremely strong
The main shaft 3 moves to the front side against the attraction force of the thrust magnetic bearing 30 due to the close contact force, and the above-described problem occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a spindle head control method capable of preventing a protective bearing from being damaged when a tool is changed.

[0023]

Means for Solving the Problems and Effects There is provided an invention according to claim 1 of the present invention for solving the above-mentioned problems.
A thrust magnetic bearing and a radial magnetic bearing for rotatably supporting the main shaft, a protective bearing for rotatably supporting the main shaft in an emergency, and the protection bearing is fixed to the main shaft, and the main shaft moves to the front side in the axial direction. An engagement member that engages with a protective bearing to restrict movement of the main shaft, and the thrust magnetic bearing,
A spindle head having a housing for fixing and supporting the radial magnetic bearing and the protective bearing; bearing control means for controlling the operation of the thrust magnetic bearing and the radial magnetic bearing; and replacing a tool mounted on the spindle with a new tool A method of controlling the operation of the spindle head of a machine tool having a tool exchange means to perform, at least at the time of tool exchange by the tool exchange means, to move the spindle to the front side in the axial direction,
The operation of the spindle head is controlled such that the engagement member and the protective bearing are engaged with each other to restrict the movement of the spindle to the front side in the axial direction.

According to the present invention, at least at the time of tool change by the tool changing means, the main shaft is moved to the front side in the axial direction, and the engaging member and the protection bearing engage to move toward the front side in the axial direction of the main shaft. When the used tool mounted on the spindle is pulled out by the tool changer, even if a load in the pulling direction acts on the spindle due to the close contact between the tool taper section and the spindle receiving section. Since the mating member and the protective bearing are already engaged, the main shaft does not move to the front side in the axial direction, thereby causing a conventional problem that the protective bearing is damaged by collision between the two. Can be prevented.

That is, when the tool is pulled out from the main shaft, the load acting on the protective bearing is a static load when the engaging member and the protective bearing are engaged, and the dynamic force acting as the main shaft moves. Since the value is smaller than the load, damage to the protective bearing can be prevented.

According to the second aspect of the present invention, the movement of the spindle during the above-mentioned tool change can be performed simply, efficiently and reliably. That is, the invention according to claim 2 is characterized in that, in the invention according to claim 1, at least at the time of tool exchange by the tool exchange means, the main shaft is moved to the front side in the axial direction by the attraction force of the thrust magnetic bearing. And

According to a third aspect of the present invention, there is provided a main shaft, a thrust magnetic bearing and a radial magnetic bearing for rotatably supporting the main shaft, a protective bearing for rotatably supporting the main shaft in an emergency, and the thrust. A spindle head having a housing for fixing and supporting a magnetic bearing, a radial magnetic bearing and a protective bearing, a bearing control means for controlling the operation of the thrust magnetic bearing and the radial magnetic bearing, and a tool mounted on the spindle. A tool exchange means for exchanging a tool with a tool, wherein an engagement portion that engages with the protective bearing and regulates movement of the spindle when the spindle is moved forward in the axial direction is formed on the spindle. A method for controlling the spindle head of a machine, wherein the spindle is moved to the front side in the axial direction at least at the time of tool change by the tool changing means, and is kept in contact with an engagement portion of the spindle. A bearing brought engagement, so as to regulate the movement in the axial direction front side of the main shaft, it is characterized in that for controlling the operation of the spindle head.

According to the present invention, at least at the time of tool change by the tool changing means, the main shaft is moved to the front side in the axial direction, and the engaging portion of the main shaft and the protective bearing are engaged with each other. The movement to the axial front side is restricted.

Therefore, according to the present invention, the above-mentioned claim 1 is also provided.
As in the invention according to the invention, when the used tool mounted on the spindle is pulled out by the tool changing means, even if a load in the pulling direction acts on the spindle due to the close contact between the tool taper portion and the spindle receiving portion, the spindle shaft Since the joint portion and the protective bearing are already engaged, the main shaft does not move to the front in the axial direction, and it is possible to prevent a problem that the protective bearing is damaged due to collision between the two. Can be.

According to the fourth aspect of the present invention, the movement of the spindle during the above-mentioned tool change can be performed simply, efficiently and reliably. That is, the invention according to a fourth aspect is characterized in that, in the third aspect of the invention, at least at the time of tool exchange by the tool exchange means, the main shaft is moved to the front side in the axial direction by the attraction force of the thrust magnetic bearing. And

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spindle head control method according to a specific embodiment of the present invention will be described below. The configuration of the machine tool to be controlled in this embodiment is the same as that of the conventional vertical machining center 1 except that the function of the bearing control means 41 constituting the conventional vertical machining center 1 shown in FIG. The same is true. Therefore, a detailed description of the configuration and functions is omitted.

First, the bearing control means 41 receives a tool change start signal from a tool change means (not shown) or a numerical control device provided separately, and supplies the same to the rear stator 32 of the thrust magnetic bearing 30. The power is reduced and the suction force is reduced, and the power supplied to the front stator 35 is increased to increase the suction force.

In a normal state, the main shaft 3 is axially supported by a thrust magnetic bearing 30 so as to be located at a neutral position thereof, and a screw is provided at the rear end of the main shaft 3 as shown in FIG. A predetermined gap t is formed between the fitted nut 9 and the rear angular contact ball bearing (protective bearing) 8, but due to the increase in the attraction force of the front stator 35 described above, FIG. As shown, the main shaft 3 moves in the axial front side, that is, in the direction shown by the arrow, and the nut 9 contacts the rear angular ball bearing 8.

Next, after the used tool T mounted on the main shaft 3 is pulled out from its receiving portion by the operation of the tool changing means (not shown), a new tool T is mounted on the main shaft 3. At this time, even if a load in the pull-out direction acts on the main shaft 3 due to the close contact between the tapered portion of the tool T and the receiving portion of the main shaft 3, the nut 9 and the rear angular ball bearing 8 have already contacted and engaged. Therefore, the main shaft 3 does not move further to the front side in the axial direction, and the load acting on the rear angular contact ball bearing 8 becomes a static load having a smaller value than the dynamic load. As a result, the collision between the nut 9 and the rear angular ball bearing 8, which has conventionally been a problem, can be prevented, and the rear angular ball bearing 8 can be prevented from being damaged.

The timing at which the suction force of the front stator 35 is increased upon receipt of the tool change start signal and the nut 9 is brought into contact with the rear angular ball bearing 8 is determined even after the rotation of the main shaft 3 is stopped. Alternatively, it may be any state in a state where it is not stopped.

After finishing the tool change as described above,
The bearing control means 41 restores the power supply to the thrust magnetic bearing 30 so that the spindle 3 is supported in the axial direction at the neutral position.

Although the embodiments of the present invention have been described above in detail, it is needless to say that specific embodiments of the present invention are not limited to these embodiments.

For example, as shown in FIG. 2, a large diameter portion (engaging portion) 3a is formed between the flange portion 7 and the front angular ball bearing 5 at the front end of the main shaft 3, and this large diameter is formed. A predetermined gap t between the portion 3a and the front angular contact ball bearing 5
In the machine tool in which is formed, at the time of tool exchange, the main shaft 3 is moved to the front side in the axial direction in the same manner as described above, so that the large diameter portion 3a and the front angular ball bearing 5 are connected. What is necessary is just to make it contact. Even in this case, similarly to the above example, when the tool is changed, the front angular contact ball bearing 5 is required.
Can be a static load, and the front angular contact ball bearing 5 can be prevented from being damaged.

As shown in FIG. 3, a tapered portion (engaging portion) 3b is formed at the front end of the main shaft 3 on the front side from the flange portion 7, and the inner peripheral surface of the inner race 5'a is formed. In a machine tool in which a tapered front angular ball bearing 5 'is provided at a position corresponding to the tapered portion 3b, and a predetermined gap is formed between the tapered portion 3b and the inner ring 5'a. When the tool is changed, the spindle 3 is moved to the front side in the axial direction in the same manner as described above, and the tapered portion 3b and the inner peripheral surface of the inner ring 5 'of the front angular ball bearing 5' are brought into contact with each other. It suffices to make contact and engagement. Also in this case, the load received by the front angular contact ball bearing 5 'at the time of tool change can be a static load, and the front angular contact ball bearing 5' can be prevented from being damaged.

In the above example, the movement of the spindle 3 at the time of tool change is performed by adjusting the power supplied to the thrust magnetic bearing 30 and increasing the attraction force of the stator 35. However, the present invention is not limited to this. For example, the main shaft 3 can be moved using an actuator such as a hydraulic cylinder.

In the above example, the method of controlling the spindle head with respect to the vertical machining center has been exemplified. However, the present invention is not limited to this, and it is naturally applicable to a horizontal machining center (machine tool). it can.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method of controlling a spindle head according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for describing a method of controlling a spindle head according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram for describing a method for controlling a spindle head according to another embodiment of the present invention.

FIG. 4 is a front view partially showing a main part of a conventional vertical machining center in a block diagram centering on a spindle head part.

[Description of Signs] 1 (Vertical) Machining Center 2 Spindle Head 3 Spindle 5 Front Angular Ball Bearing 8 Rear Angular Ball Bearing 10 Rear Radial Magnetic Bearing 20 Front Radial Magnetic Bearing 30 Thrust Magnetic Bearing 32 Rear Stator 35 Front Stator 16 , 25, 39 Sensor 41 Control means

Claims (4)

[Claims] A main shaft, a thrust magnetic bearing and a radial magnetic bearing rotatably supporting the main shaft, a protection bearing rotatably supporting the main shaft in an emergency, and fixed to the main shaft;
An engaging member that engages with the protective bearing when the main shaft moves to the front side in the axial direction to restrict the movement of the main shaft, and a housing that fixes and supports the thrust magnetic bearing, the radial magnetic bearing, and the protective bearing. A spindle head having: a bearing control means for controlling the operation of the thrust magnetic bearing and the radial magnetic bearing; and a tool exchange means for exchanging a tool mounted on the spindle with a new tool. A method for controlling the operation of a spindle head, comprising: at least at the time of tool exchange by the tool exchange means, moving the spindle to the front side in the axial direction, engaging the engaging member with a protective bearing, A method of controlling a spindle head, comprising: controlling an operation of the spindle head so as to restrict movement to an axial front side. 2. The method of controlling a spindle head according to claim 1, wherein at least at the time of tool exchange by said tool exchange means, the main shaft is moved to the front side in the axial direction by the attraction force of the thrust magnetic bearing. 3. A main shaft, a thrust magnetic bearing and a radial magnetic bearing rotatably supporting the main shaft, a protection bearing rotatably supporting the main shaft in an emergency, and fixing the thrust magnetic bearing, the radial magnetic bearing and the protection bearing. A spindle head having a supporting housing, bearing control means for controlling the operation of the thrust magnetic bearing and the radial magnetic bearing, and tool exchange means for exchanging a tool mounted on the spindle with a new tool; A method for controlling the spindle head of a machine tool having an engagement portion that engages with the protective bearing when the spindle moves to the front side in the axial direction and regulates the movement of the spindle. At least at the time of tool change by the tool changing means, the main shaft is moved to the front side in the axial direction to engage the engaging portion of the main shaft with the protective bearing, and So as to regulate the movement in the direction the front side, the control method of the spindle head, characterized by controlling the operation of the spindle head. 4. The control method for a spindle head according to claim 3, wherein at least at the time of tool exchange by said tool exchange means, the main shaft is moved to the front side in the axial direction by the attraction force of the thrust magnetic bearing.